Stellar reflex motion
= Stellar reflex motion
The motion of a <star> around the <astronomical barycenter> caused by an orbiting companion. In an isolated <two-body problem> with relative <semi-major axis> $a$, the stellar <semi-major axis> is $a_\star=M_pa/(M_\star+M_p)$. <Doppler spectroscopy> measures its line-of-sight <velocity> and <astrometry> measures its projected position on the sky.